module: simplify --inspect-brk handling

Previously in the CommonJS loader, --inspect-brk is implemented
checking whether the module points to the result of re-resolving
process.argv[1] to determine whether the module is the entry point.
This is unnecessarily complex, especially now that we store that
information in the module as kIsMainSymbol. This patch updates
it to simply check that symbol property instead.

lib/internal/modules/cjs/loader.js

@@ -1530,32 +1530,7 @@ Module.prototype._compile = function(content, filename, format) {
     return;
   }
 
-  // TODO(joyeecheung): the detection below is unnecessarily complex. Using the
-  // kIsMainSymbol, or a kBreakOnStartSymbol that gets passed from
-  // higher level instead of doing hacky detection here.
   let inspectorWrapper = null;
-  if (getOptionValue('--inspect-brk') && process._eval == null) {
-    if (!resolvedArgv) {
-      // We enter the repl if we're not given a filename argument.
-      if (process.argv[1]) {
-        try {
-          resolvedArgv = Module._resolveFilename(process.argv[1], null, false);
-        } catch {
-          // We only expect this codepath to be reached in the case of a
-          // preloaded module (it will fail earlier with the main entry)
-          assert(ArrayIsArray(getOptionValue('--require')));
-        }
-      } else {
-        resolvedArgv = 'repl';
-      }
-    }
-
-    // Set breakpoint on module start
-    if (resolvedArgv && !hasPausedEntry && filename === resolvedArgv) {
-      hasPausedEntry = true;
-      inspectorWrapper = internalBinding('inspector').callAndPauseOnStart;
-    }
-  }
   const dirname = path.dirname(filename);
   const require = makeRequireFunction(this, redirects);
   let result;
@@ -1565,9 +1540,10 @@ Module.prototype._compile = function(content, filename, format) {
   if (requireDepth === 0) { statCache = new SafeMap(); }
   setHasStartedUserCJSExecution();
   this[kIsExecuting] = true;
-  if (inspectorWrapper) {
-    result = inspectorWrapper(compiledWrapper, thisValue, exports,
-                              require, module, filename, dirname);
+  if (this[kIsMainSymbol] && getOptionValue('--inspect-brk')) {
+    const { callAndPauseOnStart } = internalBinding('inspector');
+    result = callAndPauseOnStart(compiledWrapper, thisValue, exports,
+                                 require, module, filename, dirname);
   } else {
     result = ReflectApply(compiledWrapper, thisValue,
                           [exports, require, module, filename, dirname]);